Laser printers have been marketed for several years in various forms. In use a laser beam is focussed to a spot of light which is then caused to move across a line by a system of fixed lenses and mirrors rotating on a polygon. In one type of printer the line of spots is focussed onto a photoreceptor. As the photoreceptor moves in a direction at right angles to the line of spots an area of the photoreceptor is exposed to create an electrophotographic latent image. The image is made visible with toner which is then transferred to paper and fixed to make a permanent copy. The process can be repeated to make multiple copies. The data from which the copy is formed can be generated by a computer or from an original read with some sort of read-in device such as a charge coupled (CCD) array. These techniques are well under stood, exist in the art and are available in devices available in the marketplace.
A number of laser printers on the market use the CANON laser scanner and CANON electrophotographic engine. CANON has spent much effort to create a low cost laser scanner. This has been done by the application of innovative optical design and by judicious use of manufacturing tolerances to balance performance and cost effectiveness. The result is a laser scanner capable of generating 300 spots per inch. Laser scanners capable of generating more than 300 spots per inch become increasingly expensive as the number of spots per inch increases. There is a need for a low cost device to generate 300 or more spots per inch for use in page printers and other applications.
LED print heads with 360 dots per inch are a viable alternative to the laser scanner for use in page printers. A magneto-optic and fiber optic print head can have more than 360 dots per inch and the dots can be brighter than those in an LED print head.